Conventional optical processes only permit a determination of the surface condition rather than the determination of the structures closely underneath the surface, i.e. subsurface structures. Such determination may result in faulty analyses, as the surface structure is easily exposed to external influences, both desired and undesired. Meaningful determinations of such identification, hence, structures, therefore, cannot be carried out any longer after changes in the surface. To overcome the afore-described disadvantage of the state-of-the-art capabilities of determining the texture of surfaces, it is desirable to the invention encounters the problem of determine not only the surface texture but also, at the same time, the also the structure below the surface down substructure to a depth of about one wavelength.